/*
 * ProGuard -- shrinking, optimization, obfuscation, and preverification of Java bytecode.
 *
 * Copyright (c) 2002-2018 GuardSquare NV
 *
 * This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public
 * License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later
 * version.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied
 * warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along with this program; if not, write to the Free
 * Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 */
package proguard.optimize.info;

import proguard.classfile.*;
import proguard.classfile.attribute.CodeAttribute;
import proguard.classfile.instruction.*;
import proguard.classfile.instruction.visitor.InstructionVisitor;
import proguard.classfile.util.SimplifiedVisitor;

/**
 * This InstructionVisitor marks all methods that branch backward in any of the instructions that it visits.
 *
 * @author Eric Lafortune
 */
public class BackwardBranchMarker extends SimplifiedVisitor implements InstructionVisitor {
    // Implementations for InstructionVisitor.

    public void visitAnyInstruction(Clazz clazz, Method method, CodeAttribute codeAttribute, int offset,
        Instruction instruction) {}

    public void visitBranchInstruction(Clazz clazz, Method method, CodeAttribute codeAttribute, int offset,
        BranchInstruction branchInstruction) {
        markBackwardBranch(method, branchInstruction.branchOffset);
    }

    public void visitAnySwitchInstruction(Clazz clazz, Method method, CodeAttribute codeAttribute, int offset,
        SwitchInstruction switchInstruction) {
        markBackwardBranch(method, switchInstruction.defaultOffset);

        for (int index = 0; index < switchInstruction.jumpOffsets.length; index++) {
            markBackwardBranch(method, switchInstruction.jumpOffsets[index]);
        }
    }

    // Small utility methods.

    /**
     * Marks the given method if the given branch offset is negative.
     */
    private void markBackwardBranch(Method method, int branchOffset) {
        if (branchOffset < 0) {
            setBranchesBackward(method);
        }
    }

    private static void setBranchesBackward(Method method) {
        ProgramMethodOptimizationInfo.getProgramMethodOptimizationInfo(method).setBranchesBackward();
    }

    public static boolean branchesBackward(Method method) {
        return MethodOptimizationInfo.getMethodOptimizationInfo(method).branchesBackward();
    }
}
